1. Field of the Invention
The present invention relates to zero insertion force (ZIF) connectors, especially to a ZIF pin grid array (PGA) connector including a top cover, an intermediate sliding plate and a base housing.
2. The Prior Art
PGA connectors have been developed for a long time and many U.S. Patents are related thereto. One type generally called low insertion force (LIF) connector, is described in U.S. Pat. Nos. 3,676,832, 4,498,725, 4,988,310, 5,002,499, 5,013,256, 5,057,031 and 5,092,789 wherein the contacts are embedded within the respective cavities in the base housing, and a sliding plate carries an above PGA electrical component having a plurality of conductive pin extending downward out of the sliding plate to laterally or horizontally move with regard to the base housing. The conductive pin of PGA can be downward inserted through the slide plate into the base housing without interference initially, and then laterally, i.e. horizontally, moved to engage and be sandwiched within two horizontal resilient arms of the contact in the cavity of the base housing subsequently. Such engagement between the conductive pin of the PGA component and the contact of the socket housing is in a form of low insertion force (LIF).
The second type can been seen in U.S. Pat. Nos. 5,017,152, 5,037,321, 5,059,135, 5,186,642, and 5,192,221, in which one generally vertical beam of a pair of contact beams can be moved or deflected along with the sliding or moveable plate when such sliding plate is actuated to horizontally move along the top surface of the base housing. The outwardly lateral movement of one beam of such pair of contact beams results in expansion of the space between such pair of beams so that the conductive pin of the PGA component can be inserted into the space between such pair of contact beams in the cavity of the base housing without interference, i.e., zero insertion force (ZIF). Consequently, the sliding plate moves back transversely to its original position, and the deflected beam can restore itself to the original position by its inherent resilience and cooperate with another opposite beam to electrically engage the inserted conductive pin of the PGA component therebetween.
Similar to the second type, the third type PGA connector also uses the sliding plate to movably deflect the top portion of the contact beam. Differently, the third type design generally uses a pair of sliding plates which move horizontally with regard to the base housing and in opposite directions with each other to urge such two beams of the contact in the base housing, respectively. Hence, such pair of beams are simultaneously outwardly biased to expand the opening therebetween to receive the inserted conductive pin of PGA under a ZIF condition. After the PGA pin is completely vertically loaded within two contact beams, both sliding plates move back in opposite directions relative to each other, to their original positions, respectively. Therefore, such pair of contact beams restoratively move close to each other for electrically tightly engaging the conductive pin of PGA inserted therebetween. For example, there are U.S. Pat. Nos. 4,468,072, 4,674,811, 4,836,798, 4,889,499 and 5,123,855 disclosing the similar manner.
Regardless of two-piece (i.e. one sliding plate associated with the base housing) PGA connector or three-piece (i.e. two sliding plates associated with the base housing) PGA connector, the respective designs have their individual advantages and disadvantages from the viewpoints of mechanical function, manufacturing process and economic consideration.
An object of the present invention is to provide a three-piece (i.e. a sliding plate sandwiched between a cover and the base housing) PGA connector which may not only be easily and economic manufactured and assembled, but also have good function and performance in cooperation with the PGA component.